"Our bodies have not adapted to the culture we're living in now," says Brian Luke Seaward, author of "Managing Stress: Principles and Strategies for Health and Well-Being." "Our response to every threat — whether it's a saber-toothed tiger or a divorce or an approaching deadline — is fight or flight."

"We see an increase in our heart rate, blood pressure, breathing rate — basically all the metabolic activities that get you to survive and run for the hills," Seaward says.

"Once the lion is gone, your stress response subsides" says Massachusetts Institute of Technology instructor Thea Singer, author of "Stress Less: The New Science That Shows Women How to Rejuvenate the Body and the Mind." "So much of what stresses us now, though, is perceived stress. And when you constantly perceive yourself as stressed, your stress hormones never get turned off and you bathe yourself in a toxic substance."

This toxic substance is made up mostly of epinephrine, norepinephrine and cortisol — hormones produced by the adrenal cortex in response to stress. This is fantastic when you need to jump out of the path of a careening vehicle. Not so fantastic when a Twitter blackout sends you into apoplexy.

Which raises the question: Can we reset our body's response to stress?

"There are things you can do so you will be less reactive to a stressor when one hits," she says. "It's really important to be proactive."

Break a sweat

Exercise, widely touted as a healthy outlet after stress hits, also protects the body from flying unnecessarily into crisis mode at the first sign of trouble.

"Exercise is a good stressor," Singer says. "It gives your neurons a tiny little assault and they thicken in response, so they can better withstand a bigger assault."

So hitting the treadmill will make life's unexpected traffic jams less taxing on your brain and organs.

It also trains your brain to relax, says Seaward.

"When athletes engage in exercise they have a parasympathetic rebound," he says. "When they stop, their bodies say, 'It's time for relaxation' and they kick in a chemical called acetylcholine, also known as a relaxation hormone. If you look at our culture, we're not exercising regularly. We're training ourselves for stress, but we're not training ourselves for relaxation."